Ignition diagnostics

While reading thru all the posts here (I'm up to page 65) I read multiple advice posts instructing the OP to test the coil and points with a multimeter to get test readings.

It occurred to me yesterday that I don't honestly understand whats going on here.

Yup, I have several engines around here...diesel, they have no ignition system per se, and small engines that all have magneto ignitions. The skid steer, the small tractors to move stuff around (a collection of wheel horses, with wagons dozer blades and front end loaders) serve most jobs due to the tight spaces around the cow yards and woods. The only coil&points ignition was on a big skidder we sold and it never gave us any problems to fix. In my youth I did have a bunch of cars and trucks with C&P ignitions, and I repaired em all the time.

That was.... al long time ago. I think the last C&P ignition I had here to fix was back in the early 80s.

So it being 2022, I seem to have forgotten most of the stuff I used to know without thinking much about it. A few life threatening head injuries over the yrs didnt help much :roll:

So, I got Jmor's wire charts (nice job btw) and they are great. Is there some flow charts or instructions around here on how to properly test the 12v converted 8n side mount distributor system? What to check on the coil where ect ect... I could really use those.

I have the ford "tractor electrical diagnosis manual" but it seem to be all for 6v pos ground systems (or, I missed something) and mentally swapping from 6v to 12v and pos to neg ground reference on the fly makes my damaged brain cells misfire.

What I need is a modern version of the diagnosis manual written for 12v neg ground side mount systems.

I have the tools, multimeters, dwell meters, timing lights, test lights circuit probes... all kinda stuff in the cabinet but... I've kinda lost the skill to use em over the yrs of not needing to.

That and the old head injuries.... I tend to forget stuff I should know or remember it wrong sometimes. well written manuals save my butt.

So yeah... an 8n diagnosis manual for 12v side mount C&P systems... how to... charts or something I can keep in the manuals to refer to every 5 min. :lol:

What do you fella have and where is it?

Thanks!

I say that techniques are the same, pos or neg ground. In fact, just don't even think of pos vs neg, just chassis and all else. Now when you need to connect an instrument, the red lead is pos & the other (usually black) is neg. So, if pos gnd connect red lead to chassis , but if neg ground, connect black to chassis.
The test lamp doesn't care.

As JMOR said,all systems that use points and coil for ignition are besically the same. I have been working
on old style ignitions,changing points,plugs and etc since the late '60s when almost all motors were point
systems. I used to use rolling papers to determine the timing with a slight tug on the paper while turning
the distributor. When the points lose their grip,that's when they would send the signal to the points. This
would work on these as well,but a multimeter gives an easier result,and I don't keep papers around these
days. Most problems withg power to the coil will be a loose connection or a wire connected wrongly. The
ignition switch is also a problem in the N tractors,but I've also had the problem with old Ford trucks as
well.

Nyquil Man-
I did a new lengthy thread on FORD electrical systems two posts above. See if this helps answer your questions.

Tim Daley(MI)

Yeah that is an impressive amount of info there in one post. Thanks!

So When they won't start, the first step is...

Pick a wire diagram that matches your tractor model, and make sure everything is properly wired, clean and tight.

Seems like a good place to start in any case.

My OP here probably is just looking for an updated troubleshooting flow chart with more details than I probably need.

Like the coil question, how to test it. Its kind of a trick question. You can test it all you like, but it doesn't mean its a good coil once either warmed up, shaken or whatever variable you want to subject it to. For example, my 88 toyota truck runs perfect 363 days a yr, but the other day I turned the key and it was all spin and no fire. I found no spark, so I tested the coil, seemed to have the normal ohms, so I figured it was good. I put it back on and for some oddball reason it started right up. It did that for a couple days. Then it started being stubborn starting. I popped the hood and give the coil a light whack with wrench.

Then it started right up and ran fine all day.

So... there ya go. Cheapo Adavance Auto parts.

anywho thanks for all the info, I'll print it all out and your post and stick it in my ever growing folder of 8N tech data.

Once my new 52ish 8n gets here, even though it runs just fine, I better take a good hard look at how its wired up....just in case whacking it with a wrench doesn't get it going one sunny day when it wont run.

You guys should make that thread a sticky. Everything you need to now about 9/2/8n wiring.

(quoted from post at 13:16:12 08/11/22) I say that techniques are the same, pos or neg ground. In fact, just don't even think of pos vs neg, just chassis and all else. Now when you need to connect an instrument, the red lead is pos & the other (usually black) is neg. So, if pos gnd connect red lead to chassis , but if neg ground, connect black to chassis.
The test lamp doesn't care.

Click to expand...

ou expressed some concerns about pos & neg ground systems............well, study this a bit. Really the same circuits either way, but since the engineers chose to use the chassis/housings as a +wire" in the circuit, one does need to connect any test equipment according to + or (-), regardless of what one calls "ground".



































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